Fluidized Bed Gasification of Biomass and Biomass/Coal Pellets in Oxygen and Steam Atmosphere

The oxygen and steam fluidized bed gasification of wood and olive husk/coal pellets was studied with preliminary experimental investigations in a pre-pilot scale bubbling fluidized bed reactor. Two different bed materials were adopted: inert quartzite and Ni-alumina catalyst. The gasification tests were carried out at steady state, under operating conditions typical for gasification paper. The gas analyses have been performed with dedicated instrumentations, like continuous analyzer and adopting a standard protocol for tar sampling and characterization. The influence of the equivalent ratio (ER), steam oxygen ratio (SOR) and bed temperature on the concentration of stable gas (e.g. H2, CO2, CO and CH4) as well as on the efficiency of tar conversion and syngas heating value were studied. A comparison between air-steam and oxygen-enriched with steam gasification was also carried out. In particular, the oxygen enrichment of gasification atmosphere leads to highest char carbon conversion and, of course, limited dilution in nitrogen of the syngas. In contrast, the tar content is still somewhat high, even simpler tar species were detected, and a higher CO2 level is attained in the syngas.